Telephone system.



R. H. SMITH.

TELEPHONE SYSTEM.

APPLICATION FILED APR-22.1918.

Patented Feb. 18, 1919.

'w ME 1 //1 ven/or Roy H. 5/44/77) TED sTA'rEs BOY H. SMITH, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed April 22, 1918.

new and useful Improvements in Telephone Systems, of which the following is a full,

clear, concise, and exact description.

This invention relates to telephone systems, more particularly to such systems in which line circuits terminating at a central oflice are provided with multiple line signaling devices distributed before the different operators positions.

The object of this invention is the provision of a system of this type in which there is no interference between the controllin apparatus of the signals located at the di erent positions. i

In the equipment of such systems it is the common practice to provide at each of the several positions of the switchboard, a pilot relay in a conductor common to the signaling circuit of a group of lines terminating at that position. There lS'itlSO provided a signaling device termed the pilot signal, which is associated with, and controlled by the operation of the pilot relay for the purpose of directing the operators attention tothe display of the smaller and less striking in dividual line signals. 7

It has, heretofore, been found that when a large number of line signals are illuminated at one position and only a comparatively few at another position, the current flowing through the multiple line signaling circuits is of a suflicient strength to cause the pilot relay at the latter mentioned position in some cases to be maintained energized, even though all of the line signals in that position have been extinguished.

In accordance with a feature of the invention, means is provided to prevent a false operation of a signal individual to one operators position due to the operation of a, large number of line signals at another position. More specifically, in accordance with this feature of the invention, there is provided in circuit with the usual pilot relay, a marginal relay which operates when a large number of primary line signals are illuminated at one position in order that the current flow through the multiple line signaling circuits will not be of sufficient strength to defer the release of the pilot relay at another Specification of Letters Patent.

. phone line Patented Feb. 18, 1919.

Serial No. 230,188.

position when all of the line signals at that position have been extinguished, thereby preventing the false operation of the pilot signal associated therewith.

For a more complete understanding of the invention, reference should be had to the followincr description, considered in connection with the accompanying drawing form ing a part thereof, wherein is shown only that portion of a telephone system as is necessary for a clear and definite understanding of the invention.

In the drawing are shown a number of operators positions, X, Y and Z, in which are grouped a plurality of line relays individual to each of the telephone lines terminating at the several positions of the switchboard. Associated with each of the line relays is a primary line signal and a secondary line signal, the latter being illuminated at the adj acent position whenever the line relay with which it is associated is operated. At each of the several positions there is shown, in addition to the usual pilot relay and pilot lamp, a marginal relay in circuit with the pilot relay, responsive upon a predetermined fiow'of current to cause the short-circuiting of the pilot relay and to establish another circuit for the pilot lamp when the pilot relay releases. There is also shown a tele- A extending from a substation B to an answerin jack C, located at position X of the switch oard. It is understood, of course, that a plurality of such lines terminate at each of the several positions, al-

though they are not shown.

Subscriber B in initiating a call removes the receiver from the switchhook, causing the energization of the line relay 10 over a circuit extending from battery through the right-hand winding of relay 10, righthand normal contact of cutoff relay 11, substation apparatus, left-hand normal contact of cutofl' relay 11 and left-hand winding of rela 10 to ground. Relay 10 thereby attracts its armature, lighting the primary line lamp 12 and secondary line lamp 13, the former, over a circuit extending from battery through the alternate contact of relay 10, primary line lamp 12, winding of marginal relay Hand pilot relay 15 to ground. The circuit for the latter extends from battery through the alternate contact of relay 10. secondary line lamp 13, Winding of marginal relay 16 and pilot relay 17 located at the adjacent position to ground. Pilot relay 15 is thereby energized to effect the illumination of pilot lamp 18 over a circuit extending; from battery through the pilot lamp 18, alternate contact of pilot relay 15 to ground. Marginal relay 14 is, however, not operated unless the current flow through such circuit reaches a'predetermined value. Pilot relay 17 at the adjacent position is likewise operated to lightthe pilot lamp 19 over a circuit similar to that just traced.

Assuming that a large number of subscribers, whose lines terminate at position Y initiate calls by removing the receivers from their switchhooksf This causes the energization and operation of the apparatus individual to such lines, as for example, line relays 20, 21 and 22, which, on operation, effect the illumination of the primary line lamps 23, 21 and and in addition the secondary line lamps 26, 27 and 28 which are multipled to the adjacent position Z. Since there are a large number of primary line lamps illuminated in position Y, the current flow through the secondary signaling circuits extending between the positions X and Y will be of sufficient strength to maintain the pilot relay 15 energized. even though all of the calls at position X have been answered by the operator. who, in so doing, causes the operation of the cutofl' relay which opens the circuit for the line relay, whereupon the primary and secondary line lamps associated therewith are extinguished. The circuits for the line signals .are in multiple relation with respect to the pilot relays of the two positions so that the current in the individual circuits is not of a strength which is sufficient to effect the illumination of the primary and secondary line lamps. When a predetermined number of line lamps in position Y have been illuminated, relay 16 is operated, which shortcircuits pilot relay. 17 and also establishes a new circuit for the pilot lamp 19 through the right-hand alternate contact of relay 16 to ground. Since relay 16 is of a lower resistance than that of the pilot relay 17 the voltage drop across the pilot relay circuits I of the two positions, is materially reduced after all of the calls at position X have. been answered in the usual manner. The pilot relay 15 is so designed that it will not retain its armature in attracted position on this reduced current. It is, of course, un-

derstood under the conditions assumed that the operator at position Z is engaged in handling calls originating at her position, so that she is not free to attend to the calls originating at position Y which are also indicated at her position by the illumination of the secondary line lamps 26, 27 and 28.

From the above description, it is evident that by providing in series with the usual pilot relay, a relay of the type referred to, the deenergiaation of the pilot relay at the ad acent position is assured when a l of the calls originating at that position have been answered. The consequent annoyance and inconvenience to the adjacent operators is thereby avoided.

By providing a pilot relay circuit of the character as herein specified, it is not neces sary to connect symmetrically in multiple all of the several lines from the terminating position to all of the lines of other multiple positions, but they may be asymmetrically multipled to the several positions of the switchboard indiscriminately. The com- 111011 practice is, however, to have the lines multipled symmetrically to the other positions and it is therefore the preferred form of the invention.

What is claimed is:

1. A telephone system comprising a plurality of operators positions, a plurality of lines assigned to each of such positions and multipled toanother position, signals individual to said lines at both positions, circuits extending-between said positions for interconnecting said signals, a pilot signal common to the signals of each position, and means for preventing a false operation of the pilot signal at one position through said interconnecting circuits between theindividual signals at such positions.

2. A signaling system comprising a plurality of common signaling devices responbranch circuits of each main circuit with similar branch circuits of other main. circuits, whereby the closing of any branch circuit will cause a flow of current in a plurality of main circuits, and means responsive to a predetermined flow of current in one of said main circuits for rendering said interconnecting circuits ineffective with respect to more than one common signaling device.

3. A telephone system comprising a plurality of operators positions, a plurality of lines assigned to 'each of said positions and multipled to another position, signaling de vices individual to each of the telephone lines at both positions, circuits extending between adjacent positions for interconnecting said signaling devices, a pilot relay for each position, said pilot relay being common to the telephonelines terminating at that position, and means responsive to the operatlon of a predetermined number of naearaa rent in the circuit of the pilot relay of one positionto cause the release of a similar relay at another position.

5. A telephone system comprising a plurality of telephone lines terminating at the several positions of a switchboard and multipled to another position thereof, signaling devices individual to each ofthe telephonelines at both positions, a circuit extending between said positions for interconnecting said signaling devices, a pilot relay common to each position and associated with the telephone lines terminating at that position, and switching means operative in res onse to a predetermined value of current 1 thecircuit of one pilot relay to cause the release of another pilot relay.

6. A telephone system comprising a plurality of telephone lines terminating in the several positions of a switchboard, a signaling device individual to each of the telephone lines, additional signaling means multipled to an adjacent position, a pilot relay common to each position and associated with the telephone lines terminating at that position, and a marginal relay operative on a definite value of current to cause till the release of the pilot relay at an adjacent position when said line signals at that position have been extinguished.

7. A telephone system comprising a plurality of telephone lines terminating at the several positions of a switchboard, a line signal individual to each of the telephone lines and an additional signal for each of the telephone lines, said additional signal being multipled to another multiple position, a pilot relay individual to each position and associated with the telephone lines terminating at that position, and means in circuit with the pilot relay which operates on a predetermined value of current to cause the release of a pilot relay at the other position when said line signals at that position have been extinguished.

8. A telephone system comprising a plurality of telephone lines terminating at the several positions of the switchboard, a. line signal individual to each of the telephone lines, an additional signal for each of said lines said additiional signal being multipled to an adjacent position, a pilot relay individual to each position and associated with the lines terminatin at that position, and a marginal relay in circuit with the pilot relay to assure the release of the pilot relay at an adjacent position when said line signals at that position have been extinguished. Y

9. A telephone system comprising a plurality of telephone lines terminating in the several positions of a switchboard, a line signal individual to each of the telephone lines, an additional signal for each of the telephone lines, said additional signal being multipled to an adjacent position, a

pilot relay individual to each position and associated with the telephone lines terminating in that position, and a marginal relay associated with the pilot relay at each position, said marginal relay being operative on an' excessive value of current to cause the release of the pilot relay at that posi tion so as to prevent a false operatlon of the pilot relay at the adjacent position.

10. A telephone system comprising a plurality of telephone lines terminating in the several positions of the switchboard, a line signal individual to each of the telephone lines, an additional signal for each of the telephone lines, said additional signal being multipled to another position, a pilot relay individual to each position and associated with the telephone line terminating in that position, means associated with the pilot relay at each position, said means being operative on an excessive value of current to short-circuit the pilot relay at that position so as to prevent the false operation of the pilot relay at the other position.

11. A. telephone system comprising a plurality of telephone lines terminating in the several positions of the switchboard, a line signal individual to each of the telephone lines, an additional signal for each of the telephone lines, said additional signal being multipled to another position, a pilot relay and signal individual to each position and associated with the telephone line terminating in that position, and a marginal relay associated with the pilot relay at each posi' tion, said marginal relay being operated upon an excessive value of current to short-circuit the pilot relayat that position and to establish another circuit for the pilot signal therefor, the short-circuiting of said pilot relay there-by prevents the false operation of the pilot signal at the other position.

In witness whereof I hereunto subscribe my name this 18th day of April, A. D. 1918.

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